Today's high performance two-wheeled vehicle is often subjected to extreme riding conditions. Accordingly, riders expect precise steering, robust construction, and improved resistance to torsional and shear forces.
Therefore, designers seek improvements to, for example, axle technology and how axles are retained to vehicle frames.
For example, in U.S. Pat. No. 4,632,415 (San Hai), the fork ends have bearings for receiving a spindle that supports a wheel hub. The spindle is one piece and has threads on one end that, when the spindle is supported by its bearings, projects out of its bearing. A nut is then threaded onto the threaded end of the spindle to secure the spindle to the front fork. The fact that the non-threaded, enlarged end of San Hai's spindle appears to have a screwdriver slot implies this design was not meant for tool-free use and was certainly not ergonomically designed.
In U.S. Pat. No. 6,109,635 (Maeda), a motorcycle axle having a threaded end for engaging an axle nut is described. The axle nut is then clamped in a split-clamp axle holder. However, the threads of the axle never engage complementary threads of the axle holder, since there are no such complementary threads.
In U.S. Pat. No. 6,412,803 (Lalikyan), an inverted front fork and wheel assembly for bicycles and motorcycles includes an axle having non-circular end portions that are clamped within corresponding non-circular dropout openings, thereby to increase the torsional stiffness of the fork.
In U.S. Pat. No. 6,886,894 (Kanchisa), a hub axle is provided that is preferably a one-piece unitary member made from a suitable rigid material. Similar to the '415 patent mentioned above, the hub axle has threads on one end that, when the hub axle is supported by its bearings, projects out of its bearing. A nut is then threaded onto the threads of the end of the hub axle to secure the hub axle to the front fork. Also, as with the '415 patent, the fact that the enlarged end of Kanchisa's head portion is described as being a tool engaging portion, implies this design was not meant for tool-free use and was also certainly not ergonomically designed.
In U.S. Pat. No. 7,090,308 (Rose), a multi-component axle assembly for mounting a wheel to a vehicle is described. The tubular body, while having a threaded end for engaging complementary threads in one of the dropouts, has at least one slot in each end that allows radial deformation of the tubular body when the clamp lever is placed in the clamping position.
In the Rockshox TULLIO (™) system (see 2002 Rockshox Psylo U-Turn Service Guide, pp. 8-10), a simply machined tubular axle member had a threaded bearing end for capture in a threaded split-clamp pinch-bearing and a separate smooth bearing end for capture in a smoothly machined split-clamp pinch bearing. The TULLIO system included a lever for rotating the axle so that the threads of the TULLIO axle can be captured by the complementary threads of the split-clamp pinch bearing. The lever, during non-use, was pivoted until it was parallel with the longitudinal axis of the axle and then pushed into a stowed position inside the lever-retaining component. The lever-retaining component was screwed into the smooth bearing end of the tubular axle member making the TULLIO system a multi-component axle assembly. Clamps were used for opening and closing the split-clamp pinch bearings. The TULLIO system is also described in GB 2,414,971 (Bartlett).
While in GB 1,336,620 (Mannesmannrohren-Werke GMBH), a method of forming a generic axle (no application mentioned) using forging of a hollow tube is described, there appears to have been little discussion in the prior art about the methods used to manufacture motorcycle or bicycle axles and how those methods may be integrated into the axle assembly process (e.g. axle attachment to vehicle).
Some common prior art methods for manufacturing motorcycle or bicycle axles include machining a tubular or solid metallic extrusion or billet and internally and externally swaging and forming from steel tube stock. These methods are not necessarily cost effective. Additionally, these methods do not easily lead to one-piece and ergonomically shaped end products.
Accordingly, there is room for improvement within the art.